rx-player/src/parsers/texttracks/srt/native.ts

Canal+ HTML5 Video Player

/**
 * Copyright 2015 CANAL+ Group
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * /!\ This file is feature-switchable.
 * It always should be imported through the `features` object.
 */

// srt to VTTCue parser, Done for fun.
// Heavily inspired from the WebVTT implementation

import type { ICompatVTTCue } from "../../../compat/browser_compatibility_types";
import makeVTTCue from "../../../compat/make_vtt_cue";
import bufferSourceToUint8 from "../../../utils/buffer_source_to_uint8";
import { utf8ToStr } from "../../../utils/string_parsing";
import getCueBlocks from "./get_cue_blocks";
import parseCueBlock from "./parse_cue";

/**
 * Parse whole srt file into an array of cues, to be inserted in a video's
 * TrackElement.
 * @param {string|bufferSource} input
 * @param {Object} _context
 * @param {Number} timeOffset
 * @returns {Array.<VTTCue|TextTrackCue>}
 */
export default function parseSRTStringToVTTCues(
  input: string | BufferSource,
  _context: unknown,
  timeOffset: number,
): Array<ICompatVTTCue | TextTrackCue> {
  let srtStr: string;
  if (typeof input !== "string") {
    // Assume UTF-8
    // TODO: detection?
    srtStr = utf8ToStr(bufferSourceToUint8(input));
  } else {
    srtStr = input;
  }
  // Even if srt only authorize CRLF, we will also take LF or CR as line
  // terminators for resilience
  const lines = srtStr.split(/\r\n|\n|\r/);

  const cueBlocks: string[][] = getCueBlocks(lines);

  const cues: Array<ICompatVTTCue | TextTrackCue> = [];
  for (let i = 0; i < cueBlocks.length; i++) {
    const cueObject = parseCueBlock(cueBlocks[i], timeOffset);
    if (cueObject !== null) {
      const nativeCue = toNativeCue(cueObject);
      if (nativeCue !== null) {
        cues.push(nativeCue);
      }
    }
  }
  return cues;
}

/**
 * @param {Object} cueObj
 * @returns {TextTrackCue|VTTCue|null}
 */
function toNativeCue(cueObj: {
  start: number;
  end: number;
  payload: string[];
}): ICompatVTTCue | TextTrackCue | null {
  const { start, end, payload } = cueObj;
  const text = payload.join("\n");
  return makeVTTCue(start, end, text);
}